Fluidic automobile steering system which automatically compensates for wind gusts and the like

ABSTRACT

An automobile steering system having a fluidic rate sensor, a fluidic amplifier, and a closed loop fluid operated actuator to provide steering corrections to compensate for lateral disturbances such as wind gusts and road irregularities. The steering system of this invention further includes an apparatus responsive to the rate of change of driver commands for providing a signal to cancel rate sensor output signals due to course deviations induced by driver commands having high rates of change.

United States Patent [7 2] lnventor Jerome G. Rival-d Birmingham, Mich.[21 1 Appl. No. 792,243 [22] Filed Jan. 16, 1969 [45] Patented Apr. 27,1971 .[73] Assignee The Bendix Corporation 541 FLUIDIC AU'IOMOBTLESTEERING SYSTEM WHICH AUTOMATICALLY COMPENSATES FOR WIND GUSTS AND THELIKE 26 Claims, 5 Drawing Figs.

[52] US. Cl l80/79.2, 137/ 81.5 [51] Int. Cl 862d 5/08 [50] Field ofSearch 180/792, 79.1; 244/78, 77 (M); 114/144, 150; 137/815 [56]References Cited UNITED STATES PATENTS 2,579,711 12/1951 Staude 9 l/375X2,865,462 12/1958 Milliken et a1. 180/792 2,902,l04 9/1959 Schilling180/792 2,904,120 9/1959 Bidwell 180/792 3,011,579 12/1951 Milliken etal. 180/792 3,254,864 6/1966 Kent et al. 244/78 3,456,752 7/1969 Fonda180/792 Primary Examiner-Kenneth H. Betts Assistant Examiner-John A.Pekar Attorneys-William L. Anthony, Jr. and Plante, Arens, Smith &Thompson PATENTED APR 2 7 I971 SHEET 1 [IF 2 PATENTEU APR27 um SHEET 2OF 2 2 4 TV 6 m, m

TOF/VEE} FLUIDIC AUTOMOBILE STEERING SYSTEM WHICH AUTOMATICALLYCOMPENSATES FOR WIND GUSTS AND THE LIKE CROSS REFERENCE TO RELATEDAPPLICATIONS This application discloses an improvement over the devicedisclosed in the application of Lael B. Taplin and myself for A FluidicAutomobile Steering System which Automatically Compensates for WindGusts and the Like," Ser. No. 792,904 filed Jan. 15, I969.

BACKGROUND OF THE INVENTION 1. Field of the Invention Steering systemsfor automobiles, and particularly, steering systems which automaticallycompensate for lateral disturbances.

2. Description of the Prior Art Steering systems for automobiles usingelectrical components which automatically compensate for lateraldisturbances such as wind gusts and road irregularities are known in theart. These-prior art steering systems have proven to be deficient inthat they do not effectively distinguish between course deviations ofthe vehicle due to driver-steering commands and course deviations of thevehicle due to lateral disturbances. Accordingly, prior art systems tendto provide steering corrections for course deviations due todriver-steering commands as well as those due to lateral disturbances.These steering corrections oppose and thereby nullify thedriver-steering commands. It will be appreciated that this effect isundesirable.

SUMMARY OF THE INVENTION Theabove-mentioned related application of LaelB. Taplin and myself discloses a fluidic automobile steering system withmeans for distinguishing between course deviations due todriver-steering commands and course deviations due to lateraldisturbances in almost all instances. Particularly, it was found thatlateral disturbances generally occur within a predetermined range ofrates of change. Therefore, according to that invention, coursedeviations due to driver-steering commands are distinguished from coursedeviations due to lateral disturbances by providing means for cancellingsignals from the sensor which represent rates of course deviations whichare outside of the predetermined range. Accordingly, the system of theaforementioned invention is responsive only to course deviations withinthe range, and hence, the system primarily responds only to coursedeviations due to lateral disturbances.

In relatively infrequent instances, a driver-steering com mand may occurhaving a rate of change which is within the aforesaid predeterminedrange of rates of change. The present invention provides means fordistinguishing between course deviations due to driver commands withinthe aforesaid range and course deviations due to lateral disturbanceswhich are also within this range. This is accomplished by providing anapparatus responsive to driver-steering commands which generates asignal representative of rates of change of driversteering commandswithin the predetermined range which is summed with the rate sensoroutput to cancel rate sensor outputs representative of course deviationsdue to the driversteering commands which are within the range of ratesof change of lateral disturbances, i.e., the range of response of thelateral disturbance compensating system. Accordingly, the system of thisinvention will not respond to driver induced course deviations even ifthe deviations have rates of change of the same order as those caused bylateral disturbances.

For example, consider the operation of the system of theabove-referenced application wherein the compensating system is adjustedsuch that it only responds to course deviations above a predeterminedrate. It will be appreciated that if a driver-induced course deviationoccurs above the predetermined rate, the course deviation will benullified by the system of that application since it is within thesystem's response range. Considering now the operation of the apparatusof the present invention, it will be appreciated that a signal will begenerated by that apparatus in response to the exampled driver-steeringcommand which will cancel the rate sensor output caused by thedriver-steering command. Accordingly, no signal will be sent to theremainder of the system, and therefore, it will not respond to, and thusnot nullify, the exampled driver-steering command.

According to this invention, a piston and cylinder combination isprovided having the piston connected to the driver input means formovement in response thereto. The piston is provided with a bleedorifice such that the pressure in the cylinder rises only in response tomovements of the driver input means at rates which result indriver-induced course deviations having rates of change within the rangeof response of the automatic steering system. The cylinder pressure istransmitted to the rate sensor either directly or downstream thereof tocancel rate sensor output signals which represent course deviations dueto the driver-steering commands having rates of change within theresponse range of the automatic compensating system.

In view of the above, it will be appreciated that the signal generatingapparatus of this invention is most advantageously combined with asystem having means for limiting the response of an automatic lateraldisturbance compensating system to vehicle course deviations having highrates of change. Through this combination, driver-induced coursedeviations are not nullified by the system, whether they are of thenormal order (i.e., deviations of low rate which are not nullified sincethey are outside of the response range of the system), or of the lessusual, higher rate order (i.e. within the response range of the systembut which are also not nullified since they are within the range of thesignal generating system). In this regard, a high-frequency responsecutoff of the rate sensor output is not required since all high ratedriverinduced turns are accounted for by the signal-generating system ofthis invention.

lmportantly, the system disclosed herein is ideally suited forincorporation in a fluidic automatic compensating system. Hence, anautomatic compensating systemincorporating the present invention may beconstructed which utilizes inexpensive and reliable fiuidic components.A

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic illustration offluidic system according to this invention for an automobile steeringsystem which automatically compensates for vehicle lateral disturbances.

FIG. 2 is a schematic illustration of a modification of a portion of thesystem of FIG. 1.

FIG. 3 is an exploded perspective view of a limited authority rotaryactuator and summer incorporated in the system of FIG. 1.

FIG. 4 is a perspective view of an automobile steering systemincorporating the lateral disturbance compensating system of FIG. 1.

FIG. 5 is a detailed view of a portion of the steering system of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a system 10is shown for automatically compensating for vehicle lateraldisturbances. The system 10 includes a course deviation sensor 12, asystem 14 for generating a signal in response to high rates of drivercommands for opposing those signals of the sensor 12 created by the highdriver command rate, an amplifying circuit 16, and an actuator 18. Inthe preferred embodiment, the automatic lateral disturbance compensatingsystem 10 includes a circuit 20 for limiting the response of the system10 to course deviations having rates of change above a predeterminedrate of change.

The course deviation sensor 12 may be a vortex rate sensor whichreceives pressurized fluid from a source 22, and upon lateral coursedeviations of a vehicle, will generate a dif ferential pressure betweenlines 24 and 26 which is representative of the direction and amount ofangular velocity of the vortex rate sensor 12 about its axis 28. Vortexdevices of this nature are well known in the art and are illustrated inUS. Pat. No. 3,351,080, and application, Ser. No. 547,595, assigned tothe assignee of this inventionv For one example, the rate sensor 12 mayhave a vortex chamber 29 including a porous ele ment 30 through whichsupply fluid passes to an axial outlet opening 32. Rotational motion ofthe vortex rate sensor 12, produced by a course deviation of thevehicle, is imparted to the supply fluid by the porous element 30thereby causing vortical flow in the device which may be measured at theoutlet opening 32. One device for measuring vortical flow at the outletopening consists of a pair of tangentially oriented pickoff tubes 34 and36 positioned near the outlet opening 32, each of the tubes receiving aportion of the vortical flow. lt can be seen from FIG. 1 that arotational flow in the clockwise direction will cause a pressure rise atpickoff 34 and a pressure drop through aspiration at pickoff 36.Consequently, a pressure differential is created between lines 24 and 26with the higher pressure being in line 24. It can also be seen that acounterclockwise flow will cause a pressure rise at pickoff 36 and apressure drop at pickoff 34 thereby causing a pressure differentialbetween lines 24 and 26 with the higher pressure in line 26. As it willbe appreciated by those skilled in the art, other rate-sensing devicesare available to sense course deviations f a vehicle. For example, rateand acceleration sensors, both angular and rectilinear, may be used,singularly or in combination.

The signal-generating system 14 includes a housing 40 having acylindrical chamber 42 therein. A piston 44 cooperates with the wall 45of the cylindrical chamber 42 to form a dynamic seal thereby dividingthe cylindrical chamber 42 into a first chamber portion 46 and a secondchamber portion 48. The piston 44 may be suitably replaced by otherdynamic seals such as a diaphragm or the like. An orifice 50 in piston44 communicates the two chamber portions each with the other. lt will beappreciated that the orifice 50 may also be located in the housing 40.The signal-generating system 14 is provided with a source 52 of supplyfluid communicating with chamber portions 46 and 48 through flow lines54 and 56, respectively. A pair of output ports 58 and 60 communicatewith output flow lines 62 and 64, respectively.

The orifice 50 is sized, both in diameter and length, such that thesignal-generating system 14 provides output signals only in response torates of movement of piston 44 above a predetermined rate. The size ofthe orifice 50 controls its flow resistance and hence the amount ofpressure differential rise between chamber portions 46 and 48 occun'ngas a result of movements of piston 44. It will be appreciated thatincreasing the diameter or reducing the length of the orifice 50decreases its flow resistance and hence increases the rate at which thepiston 44 must move to create a given output signal, and vice versa. ltwill also be appreciated that the signal-generating system 14 isresponsive to the rate of movement of piston 44 rather than the amountof movement by virtue of the orifice 50. Furthemiore, by virtue of theorifice 50, signal-generating system 14 is substantially unresponsive torates of change of course correction below a predetermined nominal rateof change.

The output flow lines 62 and 64 are connected to control ports 66 and68, respectively, of the vortex rate sensor 12 for summing the generatedsignal with sensed course deviations. The .control ports 66 and 68 aredisposed interior of the porous element 30 and are tangentially andoppositely oriented in a manner to influence the vortical flow of fluidin the vortex rate sensor 12 in opposite directions and thereby modulatethe sensor output signal according to the generated signal on lines 62and 64. 1

Alternatively, the generated signal on flow lines 62 and 64 may besummed with the rate sensor output downstream of the rate sensor 12, forexample, by supplying the signal to opposing control ports inajet-on-jet device as shown in FIG. 2 in which the jeton-jet device ofthe response-limiting circuit 20 is provided with an additional pair ofopposing control ports 70 and 72 for modulating the output signal of therate sensor according to the generated signal on lines 64 and 62,respectively.

The piston 44 is operably connected the the driver input means forreceiving driver-steering commands, for example, by a linkage 74pivotally connected to a lever 76 which rotates with the main steeringunit output shaft 78. Accordingly, the piston 44 is axially movable incylinder 42 in response to driver-steering commands.

It will be appreciated that the rate of turning or driver coursecorrection of the vehicle is a function of the angular position of thesteering wheel. Therefore, the rate of change of turning or the rate ofchange of yaw rate is a function of the angular rate of the steeringwheel movement. Accordingly, the movement of the lever 76 is inproportion to the rate of change of turning or rate of change of drivercourse correction of the vehicle. Since the lever 76 is connected to thepiston 44, the movement of piston 44 in chamber 42 is in proportion tothe rate of change of turning or rate of change of course drivercorrection of the vehicle, Hence, a fluid signal is provided by thesignal-generating system 14 in response to rates of change of drivercourse corrections of the vehicle which are above a predetermined rateof change set by the size of the orifice 50 in piston 44.

The circuit 20 for limiting the response of the system 10 to coursedeviations having rates of change above a predetermined rate of changeis essentially a proportional jet-on-jet device 80 adapted to canceloutput signals from the sensor 12 which represent course deviationshaving rates of change below the predetermined rate of change.Particularly, the jeton-jet device 80 has a supply port 82 connected toa source 84 of pressurized fluid, a first pair of control ports 86 and88 connected directly to the output of the vortex rate sensor 12 bylines 90 and 92, a second pair of control ports 94 and 96 connected tothe vortex rate sensor 12 by lines 98 and 100, respectively. Each line90 and 92 has a restriction 101 and each line 98 and has a volume orfluid capacity 102 and a restriction 104. In the case of incompressiblefluids, the volumes 102 are provided with flexible diaphragms 103 whichprovide a space for containing a compressible medium 105 which, forexample, may be air. ln the case of a compressible fluid such as air,the flexible diaphragms 103 are not necessary. The restrictions 101 maybe adjustable to balance the control flows of the circuit 20. Theproportional jet-on-jet device 80 is also provided with a pair of outputchannels 106 and 108. It will be appreciated by those skilled in the artthat the supply flow from supply port 82 will be diverted to the outputchannel 106 in response to a flow from either control port 88, controlport 96, or both, and further that the supply flow will be diverted tooutput channel 108 in response to a flow from either control port 86,control port 94, or both. The device described herein is a proportioningdevice, and therefore, the amount of flow diverted to one or the otheroutput channel depends upon the relative amount of flow from the controlports. Moreover, opposing flows from the control ports on opposite sidesof the device will have a net effect which is proportional to thedifference in their flows. That is to say, if the flow from control port86 is greater than the flow from control port 88, the supply flow fromsupply port 82 will be diverted from output channel 108 in proportion tothe difference between the flows from control ports 86 and 88. On thehand, if the flow from each of the control ports are equal, the flow tothe output channels 106 and 108 will be equal and therefor the netsignal from the device 80 will be zero.

It will be appreciated by those skilled in the art that signals havinghigh rates of change will be substantially attenuated in rate by thevolumes 102 since the capacities of the volumes tend to delay andflatten signals of high rate. It will further be appreciated that theattenuation in rate provided by the volumes 102 renders the signalshaving high rates of change passing through lines 98 and 100 relativelyineffective in diverting the supply flow in the device 80. On the otherhand, the flows through lines 90 and 92 having low rates of changepasssubstantially unimpeded.

in practice, a transition range exists between those signals havingrates of change which are substantially impeded by the restrictions 104and the volumes 102 and those signals which are not impeded. Even thougha transition range exists, this range or cutoff point may be definedappropriately as a nominal predetermined rate of change. The optimumnominal predetermined rate of change is normally set by analysis of theactual performance characteristics of the given vehicle type. Once adesired predetermined rate of change has been determined, the passagesize of restriction 104 and the capacity of volume 102 may be adjustedto provide that nominal rate. For example, either an increase in thecapacity of the volume 102 or a decrease in the passage size ofrestriction 104 will lower the predetermined rate of change, and viseversa.

Considering now a fluid signal on lines 24 and 26 representative ofcourse deviations having rates of change below the predetermined rate ofchange, i.e., due to normal driver commands, it will be appreciated thatthe signal will be substantially unimpeded by the volumes 102 in lines98 and 100, as explained above. Since the same signal passes unimpededthrough the lines 90 and 92, equal signals will be placed in oppositionin the device 80 such that the net output from the device 80 will bezero. Considering now a fluid signal on lines 24 and 26 representativeof course deviations having rates of change above the predeterminedrate, it will be appreciated that the signal will be impeded by thevolumes 102 and thereby rendered ineffective in lines 98 and 100.However, the signal will pass unimpeded on lines 90 and 92 to the device80. Accordingly, the device 80 will respond to the signals on lines 90and 92 thereby providing output signals in output channels 106 and 108which is representative of course deviations having rates of changeabove the predetermined rate of change.

For reasons which will be apparent in view of the discussion of theoperation of the system which appears below, it is often desirable topreset the aforementioned predetermined rate of change of theresponse-limiting circuit 20 to be substantially equal to theaforementioned predetermined rate of change of the signal-generatingsystem 14 since the effects of each are mutually cooperative indistinguishing course deviations due to driver-steering corrections fromcourse deviations due to lateral disturbances. Particularly, it has beendiscovered that typical driver-steering commands provide coursedeviations at rates of change below the predetermined rate whereas mostlateral disturbances create course deviations at rates of change abovethe predetermined rate. Therefore, the response-limiting circuit 20nominally distinguishes between the two types of course deviations.However, some driver course corrections will occur at rates of changeabove the predetermined rate, for example, course corrections arisingout of emergency situations. It will then be appreciated that theresponse-limiting circuit 20 will not distinguish those coursedeviations from course deviations due to lateral disturbances. However,the signal-generating system 14 does adequately distinguish these typesof course corrections. This is accomplished by canceling rate sensoroutputs due to course deviations derived from high rate of changedriversteering commands. Accordingly, the system according to thisinvention responds substantially only to those course deviations whichare due to lateral disturbances regardless of the rate of coursecorrection by the vehicle operator.

It will be appreciated that the signal-generating system 14 generallyprovides a short duration signal and therefore is ideally suited forcompensating for high rate of change, short duration, steering commandsencountered in typical emergen- -cy situations. Signal durations may beadjusted by appropriate linkages which control the excursion of thepiston 44 in the cylinder 42.

The amplifying circuit 16 comprises a fluidic amplifier 110 and a pairof variable restrictions 112. It will be appreciated that the variablerestrictions 112 may be used to adjust the gain of the signal passingtherethrough, for example, to tailor the system 10 to suit thecharacteristics of individual vehicles.

The fluidic amplifier is a jet-on-jet proportional device having asupply port 114 connected to a source 116 of pressurized fluid, a pairof control ports 118 and 120, a pair of feedback ports 122 and 124, anda pair of output channels 126 and 128 connected to output lines 130 and132. Although only a single amplifier is shown, it will be understoodthat a series of amplifiers may be used. It will be appreciated that theoutput signal on output channels 130 and 132 is an amplified signalwhich is representative of the control signal flow through control ports118 and and a feedback flow through the feedback ports 122 and 124. Tofacilitate the teaching of the present invention, the feedback systemwill be considered inoperative at the present time. it is understoodthen that the net output from the response'limiting circuit 20 isamplified by the amplifying circuit 110 to provide an amplified outputsignal on flow lines and 132 which is representative of coursecorrections required to compensate for course deviations due to lateraldisturbances sensed by vortex rate sensor 12.

The limited authority actuator 18 is adapted to be interposed in thevehicle main steering system, for example, as shown in P10. 4, toprovide steering corrections supplemental to the operator-steeringcommands. The actuator 18 (FIG. 1) comprises a spool valve 134, anactuator output portion 136 and a feedback system 138.

The spool valve 134 comprises a housing 140 and a spool 142 beingaxially movable therein in response to fluid signals on amplifiercircuit output lines 130 and 132. A source 144 of pressurized supplyfluid communicates with a central supply chamber 146 formed by thehousing 140. The spool 142 is provided with lands 148, 149 and 150cooperating with the walls of housing 140. A pair of annular returnchambers 152 and 154 are formed in the housing 140 having returnpassages 157 and 159, respectively, communicating therewith. Forexample, the return passage may be connected to a supply reser voir byflow lines (not shown). The housing 140 is further provided with a pairof output passages 156 and 158 having openings between the returnchambers and the supply chambers. Spool valves of this construction arewell known in the art and therefore only a brief description of theoperation of the spool valve 134 will follow. Assuming that the fluidflows and consequently the pressures in the lines 130 and 132 are equal,the spool 142 will be balanced in a central position thereby positioningthe spool lands 148, 149 and 150 to prevent any substantial flow betweenthe output passages 156 and 158, and either the supply chamber 146 orthe return chambers 152 and 154. If, however, there is a differentialflow between the lines 130 and 132 because the course of the vehicle hasbeen laterally disturbed, a differential pressure is established acrossthe spool 142 which causes it to move in one direction, communicatingone of the output passages 156 or 158 to the supply chamber 146 therebyallowing flow from the source 144 of supply fluid to the selected one ofthe output passages 156 or 158. Moreover, the above movement of thespool 142 communicates the other of the output passages to thecorresponding return passages 157 or 159.

The output passages 156, and 158 of spool valve 134 commanicate with theactuator output portion 136 which comprises a housing 160 and arotatable member 162 therein fixedly connected to the actuator outputshaft 164. As shown in FIG. 1, the circular sides of the rotatablemember 162 cooperate with the walls of the housing 160 to form asubstantial fluid seal therewith. The operating relationship of thehousing 160, the rotatable member 162 and the actuator output shaft 164may be more easily seen in the exploded view of these components in FIG.3.

The actuator output portion 136 responds to fluid signals from passages156 and 158. Particularly, the housing 160 is provided with a pair ofports 166 and 168, connected by a passage not shown, communicating withthe spool valve output passage 156 and is further provided with a pairof ports 170 and 172, also connected by a passage not shown,communicating with the spool valve output passage 158. As can be seen inFIG. 1, a pressure in the line 156 causes a corresponding pressureagainst the sides 174 and 176 of the rotatable member 162 causingclockwise rotation of that member whereas a pressure in the line 158causes a pressure against the sides 178 and 180 of the rotatable member162 causing counterclockwise rotation. The rotation of the rotatablemember 162 causes corresponding rotation of the actuator output shaft164.

ln HO. 1, it can be seen that the rotatable member 162 is provided withan integral extension 182, and a pair of flow nozzles 184 and 186positioned on opposite sides of the extension 182. The nozzles 184 and186 communicate with a source 188 of pressurized fluid through a pair ofrestrictions 190 and 192, respectively. The housing 160 is provided witha return passage 193 for egress of fluid from the nozzles 184 and 186.The return passage 193 may be connected to a supply reservoir. lt willbe appreciated that the rotation of the rotatable member 162, and theconsequent movement of the extension 182 with respect to the nozzles 184and 186, causes a variation in the pressure immediately upstream of thenozzles 184 and 186 due to a variation in the flow restriction at thenozzle. The pressure immediately upstream of the nozzles 184 and 186 istransmitted to the lines 194 and 196, respectively, thereby causing avariable rate of fluid flow through these lines .rom the source 188which is representative of the posi tion of extension 182, andaccordingly, the position of the actuator output shaft 164. The flowsignals in the lines 194 and 196 communicate with the feedback ports 124and 122, respectively, of the proportional amplifying device 1 10.

As can be seen in FIGS. 3-5, the housing 160 of the limited authorityactuator 18 is connected to the output shaft 78 of the main steeringunit 198 for rotation therewith. It will be appreciated then that thehousing 160 rotates in response to driver-steering commands. It can alsobe seen in FIGS. 1 and 3 that the rotatable member 162 and consequentlythe actuator output shaft 164 are allowed limited rotary movement withrespect to housing 160 by virtue of their configuration. Therefore, theactuator output shaft 164 rotates with the output shaft 78 of the mainsteering unit 198 with the exception of any relative rotation betweenthe housing 160 and the rotatable member 162.

The actuator output shaft 164 is connected to the dirigible wheels forturning of the vehicle as seen with reference to FIG. 4 in which asteering system for a land vehicle is shown having a steering wheel 200for control of the vehicle by the operator, and a steering shaft 202connecting the steering wheel 200 with a main steering unit 198.Operator commands are transmitted through the main steering unit 198 tothe main steering output shaft 78, and in'turn, to the limited authorityactuator housing 160. The limited authority actuator output shaft 164 isconnected to a Pitman arm 204 for rotation thereof. The Pitman am 204 isconnected to the dirigible wheels 212 (one not shown for clarity) by asuitable known steering linkage I 208 for turning of the dirigiblewheels 212 about the pivotal axes of the uprights 214 and consequentsteering of the vehicle. Although this invention is described withrespect to a conventional steering apparatus for an automobile, it willbe appreciated it can be equally applied to other methods for steeringland vehicles.

FIG. 5 illustrates in detail the portion of the steering system of FIG.4 having the signal-generating system 14. In FIG. 5, the housing 40 ofthe signal-generating system 14 is shown mounted on the main steeringbox 198. The lever arm 76 is also shown connected to the main steeringunit output shaft 78 an in turn connected to the piston 44 (FIG. 1)inside of housing 40 by a linkage 74 (H6. 5). The main steering unitoutput shaft 78 rotates in response to driver-steering commands on thesteering shaft 202 and accordingly moves piston 44 within housing 40 inresponse to driver-steering commands.

ln view of the above, it will be appreciated that dirver-steeringcommands are transmitted from the main steering unit output shaft 78through the limited authority actuator 18 t0 the dirigible wheels 212.However, the limited relative rotation provided between actuator outputshaft 164 and the housing 160 permits the introduction of lateraldisturbance steering corrections. This relative rotation between theactuator output shaft 164 and the housing 160 is not transmitted back tothe vehicle operator to any degree because of the low compliance of thesteering train in the reverse direction. It will thus be appreciatedthat the dirigible wheels are steered by the sum of theoperator-steering commands and the course correction signals provided byautomatic lateral disturbance compensating system 10. It will beappreciated that the operator has a wide range of authority over vehiclesteering whereas the lateral disturbance compensating system 10 has asubstantially more limited authority by virtue of the configuration ofrotatable member 162 and the actuator housing 160. However, the limitedauthority of the compensating system 10 is sufficient to correct coursedeviations due to lateral disturbances. By virtue of the limitedauthority of the lateral disturbances compensating system 10, erroneoussteering corrections die to malfunctions of the system are easilyoverriden by operatorsteering commands.

As still an additional advantage to the steering system according tothis invention, a mechanical link is provided between the steering wheel200 and the dirigible wheels 212 in the event that the automaticcompensating system 10 fails. Particularly, it will be appreciated thatthe maximum relative rotary movement between the actuator output shaft164 and the main steering system output shaft 78 is limited to only afew degrees by the configuration of the actuator housing 160. When therelative movement between the two shafts reaches its maximum limit ineither direction, the rotatable member 162 abuts against the actuatorhousing 160 thereby mechanically linking the shafts 78 and 164.Accordingly, a mechanical link is provided between the steering wheel200 and the dirigible wheels 212 in the event of the failure of thelateral disturbance compensating system 10.

To facilitate the teaching of the operation of this invention, considerthe case where a vehicle equipped with the lateral disturbancecompensating system 10 is proceeding on a straight course and does notencounter a lateral disturbance. Since the vehicle is being steered on astraight course, the piston 44 remains stationary and therefore, thereis no output from the signal-generating system 14. Also, since thevehicle is proceeding on a straight course, and consequently there is nocourse deviation, the output signal from the vortex rate sensor 12 willbe zero and hence the flows through lines 24 and 26 will be equal andconstant, i.e., a zero rate of change. Since the rate of change of thesignals on lines 24 and 26 is zero, equal signals will reach the device80 through lines and 92 and through lines 98 and 100. Accordingly, thesignals will cancel each other in the device 80, and therefore, theoutput from the response-limiting circuit 20 will be zero. Hence, theremainder of the system will receive a zero signal and therefore theoutput shaft 164 of the actuator 18 will remain stationary. It will beappreciated then that the lateral disturbance compensating system 10will have no effect on vehicle steering. This, of course, is the desiredresult since the vehicle had not encountered a lateral disturbance.

Next, consider the case where the vehicle is proceeding on a straightcourse and encounters a lateral disturbance such as a wind gust or aroad irregularity. Again there has been no driver-steering command andaccordingly there is no output signal from the signal-generating system14. However, the lateral disturbance will cause a course deviation ofthe vehicle or yaw motion of the vehicle which will be sensed by thevortex rate sensor 12. In response to the yaw motion, an output signalon lines 24 and 26 of the vortex rate sensor 12 will be provided whichis representative of the direction of the yaw motion and the yaw rate.The direction of yaw motion is represented by the fluid line, 24 or 26,which contains the highest flow rate whereas the amount of yaw rate isrepresented by the differential rates of flow in fluid lines 24 and 26.Since the deviation has been caused by a lateral disturbance, the rateof change of course deviation will be above the predetermined rate atwhich the response-limiting system 20 has been preset. Accordingly, thesignal on lines 24 and 26 from the vortex rate sensor 12 will be impededin lines 98 and 100 by the volumes 102. On the other hand, the signalwill pass unimpeded on lines 90 and 92. Therefore, as explainedpreviously, the proportional jet-on-jet device 80 will respond to theoutput signal of the vortex rate sensor on lines 90 and 92 and provide asignal corresponding thereto on its output channels 106 and 108. Inturn, the signal from the device 80 will be amplified by the amplifyingcircuit 110 and transmitted to the limited authority actuator 18. Thesignal is essentially a difference in flow rates between lines 130 and132. This difference in flow rates is applied to opposite ends of thespool 108 thereby creating differential pressure across the spool 142and a corresponding movement of the spool towards "the side of lowerpressure. This movement exposes the selected one of the output passages156 or 158 to the supply pressure in the inlet chamber 146 causing flowinto the selected passage from the source 144. Flow into these fluidpassages, as explained above, rotates the output shaft 164 in apreselected direction to provide steering of the vehicle according tothe course correction signal on lines 130 and 132, and hence, correctivesteering which compensates for the lateral disturbance.

lt can be seen from FIG. 1 that the extension 182 moves with the shaft164 to provide a flow differential between flow lines 194 and 196corresponding to the amount of actual steering correction. A flowdifferential in the lines 194 and 196 is applied to the amplifiercircuit 110 as a feedback signal. It will be appreciated that thefeedback signal opposes the input signal to the amplifier circuit 110 inproportion to the actual movement of the actuator output shaft 164thereby providing accurate position control of the output shaft 164.Furthermore, the feedback signal serves to return the actuator outputshaft 164 to the neutral position when no correction signal is receivedby the amplifier circuit 110.

Consider now the case in which the vehicle negotiates a normaldriver-induced turn (i.e., a turn having a low rate of change) and thevehicle does not encounter a lateral disturbance. Since a vehicle isnegotiating a turn, it will experience a yaw rate. The vortex ratesensor 12 will sense the yaw rate and provide an output signal on lines24 and 26 which is representative thereof. Since the vehicle isundergoing a normal driver-induced turn, the rate of change of coursedeviation will be below the predetermined rate of change at which boththe signal-generating circuit 20 have been preset. Accordingly, thesignal-generating circuit 14 will provide a zero output signal. Inaddition, the signal on lines 24 and 26 from the vortex rate sensor 12will be unimpeded by the volumes 102 and they will oppose substantiallythe same signal which is on lines 90 and 92 at the device 80. Hence, thesignals will be cancelled and the output from the device 80 on outputchannels 106 and 108 will be zero. Since the signal transmitted to theremainder of the system is zero, the lateral disturbance compensatingsystem will not provide a steering correction. It will then beappreciated that in the case of a normal driver-induced turn without alateral disturbance, the lateral disturbance compensating system 10 willhave no effect on the steering of the vehicle.

Consider now the case where the vehicle negotiates a typicaldriver-induced turn and encounters a lateral disturbance. It will beappreciated that there will be a course deviation of theve hicle due tothe lateral disturbance, and in addition, there will be a coursedeviation due to the driver-induced turning of the vehicle. These twocomponents of course deviation may either add or subtract to provide anet course deviation. The vortex rate sensor 12 will provide an outputsignal on the output lines 24 and 26 which is representative of the netcourse deviation of the vehicle. Therefore, the output signal from thevortex rate sensor 12 can be considered to have two components, acomponent representative of the course deviation due to thedriver-steering command and a component representative of the coursedeviation due to the lateral disturbance. In this regard,.thesignal-generating system 14 will have no significant effect on the ratesensor output since the driver-induced turn has a low rate of change.

As stated previously, the course deviation due to the lateraldisturbance will be at a rate higher than the predetermined rate atwhich the response-limiting circuit 20 is preset whereas the coursedeviation due to the normal driver-steering command will be at a ratebelow the predetermined rate. By virtue of this relationship, the twocomponents of the output signal from the vortex rate sensor 12 may beconsidered to be a signal of high frequency superimposed on a signal oflow frequency. The system of the present invention distinguishes the twosignals through frequency (i.e., rate of change) discrimination,accomplished by the response-limiting circuit 20. As explainedpreviously, signals from the vortex rate sensor 12 on lines 24 and 26which are representative of low rates of change are cancelled by thejet-on-jet device whereas signals representative of high rates of changeare effective in diverting the fluid flow in the device 80 such thatoutput signal from the device 80 is only representative of vortex ratesensor output signals having high rates of change. This operationaldistinction between signals having high or low rates of change persistseven though the signals are mixed. Therefore, the componentrepresentative of the course deviation of the vehicle due to the lateraldisturbance is the sole component represented in the output of thedevice 80. The output of the proportional jet-on-jet device 80 is thentransmitted to the remainder of the system 10 to provide correctivesteering of the vehicle.

Considering now the operation of the lateral disturbance compensatingsystem 10 in the event of an emergency steering command (i.e., asteering command havinga rate of change above the predetermined rate ofchange), it will be appreciated that the movement of piston 44 will besufficiently rapid so as to create a pressure differential betweenchamber portions 46 and 48 which is not immediately relieved by therestrictive flow passage 50. This pressure differential is transmittedto the vortex rate sensor 12 by flow lines 62 and 64 in a manner so asto influence the vortical flow therein and accordingly, so as tomodulate the output signal from the vortex rate sensor 12 on lines 24and 26 according to the rate of change of driver-steering commands.Particularly, the movement of piston 44 will provide a tangential jet orpulse of fluid in the rate sensor 12 which opposes vortical flow inducedby the turning of the vehicle due to the emergency driver-steeringcommand. in this manner, turning induced vortical flows due to emergencysteering commands are substantially canceled, and accordingly, thelateral disturbance compensating system 10 does not provide steeringcorrections for the emergency driver-steering commands. Therefore, theemergency driversteering commands are not nullified by the system, henceproviding the driver with full authority over the vehicle in the eventof an emergency.

in view of the above description, it will be appreciated that thepresent invention provides a low-cost and reliable fluidic lateraldisturbance compensating system. It also provides increased safety overthe steering systems of the prior art, and in addition, is more refinedin operation since it effectively distinguishes between coursedeviations due to lateral disturbances and course deviations due todriver-steering commands. All of the fluidic components described hereinare particularly adapted for efficient incorporation into a systemsuitable for automotive use. In addition, this system may be used with avariety of actuators and therefore can be conveniently incorporated withexisting steering system designs.

While I have described preferred embodiments of the present invention,it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appending claims.

lclaim:

l. A land vehicle steering system which automatically compensates forlateral disturbances comprising:

means for steering said vehicle in response to operator commands;

a sensor mounted on said vehicle and adapted to provide a sensor signalrepresentative of course deviations of said land vehicle;

means for modulating said sensor signal according to the rate of changeof said operator commands; and

means to effect the steering of said vehicle in response to saidmodulated sensor signal.

2. The steering system of claim 1 wherein said modulating means includesmeans modulating said sensor signal only according to rates of change ofoperator commands above a nominal predetermined rate of change.

3. The steering system of claim 1 wherein said sensor is a vortex ratesensor mounted on said vehicle to sense yaw rate of said vehicle.

4. The steering system of claim 3 wherein said modulating meanscomprises control port means for said vortex rate sensor for influencingan output flow therefrom according to rates of change of said operatorcommands.

5. The steering system of claim 4 wherein said control port meanscomprises a pair of control ports being tangentially oriented inopposite directions interior of said vortex rate sensor for influencingthe flow therein in opposite rotational directions in accordance withthe direction of said operator commands.

6. The steering system of claim 1 wherein said modulating meanscomprises:

means responsive to said operator commands for providing a generatedoutput signal representative of rates of change of said operatorcommands; and

. summing means associated with said sensor and said last means forproviding said modulated signal.

7 The steering system of claim 6 wherein said summing means includes aseparate device operatively associated with both said sensor and saidmeans responsive to rates of change of said operator commands forreceiving signals therefrom and providing said sum.

8. The steering system of claim 6 wherein said means providing agenerated output signal representative of rates of change of saidoperator commands comprises:

a housing;

dynamic seal means for movement in response to said operator commandscooperating with said housing to form a chamber for receiving a fluid;

orifice means communicating with said chamber for provid- Y ingrestricted flow of said chamber fluid therethrough upon movement of saiddynamic seal means; and

output means communicating with said chamber for supplying saidgenerated signal to said summing means.

9. The steering system of claim 8 wherein:

said dynamic seal means forms two chambers;

said orifice means communicates the two chambers, each with the other;and

said output means is a pair of flow passages, each communicating withthe pressure in one of said chambers, for supplyingsaid generated signalto said summing means.

10. A landvehicle steering system which automatically compensates forlateral disturbances comprising:

means for steering said vehicle in response to operator commands;

a fluidic sensor mounted on said vehicle and adapted to provide a fluidsensor signal representative of course deviations of said land vehicle;

means for modulating said sensor signal according to the rate of changeof said operator commands;

fluidic amplifier means for providing an amplified fluid signalrepresentative of said sum; and

means to effect the steering of said vehicle in response to saidamplified fluid signal.

11. The steering system of claim 10 wherein said modulating meansmodulates said sensor signal only according to rates of change ofoperator commands above a nominal predetermined rate of change.

12. The steering system of claim 10 wherein said sensor is a vortex ratesensor mounted on said vehicle to sense yaw rate of said vehicle.

13. The steering system of claim 12 wherein said modulating meanscomprises control port means for said vortex rate sensor for influencingan output flow therefrom according to rates of change of said operatorcommands.

14. The steering system of claim 13 wherein said control port meanscomprises a pair of control ports being tangentially oriented inopposite directions interior of said vortex rate sensor for influencingthe flow therein in opposite rotational directions in accordance withthe direction of said operator commands.

15. The steering system of claim 10 wherein said modulating meanscomprises:

means responsive to said operator commands for providing a generatedfluid output signal representative of rates of change of said operatorcommands; and

summing means associated with said sensor and said last means forproviding said modulated signal.

16. The steering system of claim 15 wherein said summing means includesa separate fluidic device operatively associated with both said sensorand said means responsive to rates of change of said operator commandsfor receiving signals therefrom and providing said sum.

17. The steering system of claim 15 wherein said means providing agenerated fluid output signal representative of rates of change of saidoperator commands comprises:

a housing;

dynamic seal means for movement in response to said operator commandscooperating with said housing to form a chamber for receiving a fluid;

orifice means communicating with said chamber for providing restrictedflow of said chamber fluid therethrough upon movement of said dynamicseal means; and

output means communicating with said chamber for supplying saidgenerated signal to said summing means.

18. The steering system of claim 17 wherein:

said dynamic seal means forms two chambers;

said orifice means communicates the two chambers, each with the other;and

said output means is a pair of flow passages, each communicating withthe pressure in one of said chambers, for supplying said generatedsignal to said summing means.

19. A land vehicle steering system which automatically compensates forlateral disturbances comprising:

means for steering said vehicle in response to operator commands;

a fluidic sensor mounted on said vehicle and adapted to provide a sensorsignal representative of course deviations of said land vehicle;

means for modulating said sensor signal according to the rate of changeof operator commands having rates of change above a nominalpredetermined rate of change;

means for limiting the response of said system to sensor signalsrepresentative of course deviations having rates of change above saidnominal predetermined rate of change; and

means for effecting the steering of said land vehicle according to saidmodulated sensor signals to which said system responds.

20. The steering system of claim 19 wherein said sensor is a vortex ratesensor mounted on said vehicle to sense yaw rate of said vehicle.

21. The steering system of claim 20 wherein said modulating meanscomprises control port means for said vortex rate sensor for influencingan output flow therefrom according to rates of change of said operatorcommands having rates of change above a nominal predetennined rate ofchange.

22. The steering system of claim 21 wherein said control port meanscomprises a pair of control ports being tangentially oriented inopposite directions interior of said vortex rate sensor for influencingthe flow therein in opposite rotational directions in accordance withthe direction of said operator commands having rates of change above anominal predetermined rate of change.

23. The steering system of claim 19 wherein said modulating meanscomprises:

means responsive to said operator commands for providing a generatedoutput signal representative of rates of change of said operatorcommands; and

summing means associated with said sensor and said last means forproviding said modulated signal.

24. The steering system of claim 23 wherein said summing means includesa separate device operatively associated with both'said sensor'and saidmeans responsive to rates of change of said operator commands forreceiving signals therefrom and providing said sum.

25. The steering system of claim 23 wherein said means providing agenerated output signal representative of rates of change of saidoperator commands comprises:

a housing; dynamic seal means for movement in response to said operatorcommands cooperating with said housing to form a chamber for receiving afluid; orifice means communicating with said chamber for providingrestricted flow of said chamber fluid therethrough upon movement of saiddynamic seal means; and output means communicating with said chamber forsupplying said generated signal to said summing means. 26. The steeringsystem of claim 25 wherein: said dynamic seal means forms two chambers;said orifice means communicates the two chambers, each with the other;and said output means is a pair of flow passages, each communicatingwith the pressure in one of said chambers, for supplying said generatedsignal to said summing means.

1. A land vehicle steering system which automatically compensates forlateral disturbances comprising: means for steering said vehicle inresponse to operator commands; a sensor mounted on said vehicle andadapted to provide a sensor signal representative of course deviationsof said land vehicle; means for modulating said sensor signal accordingto the rate of change of said operator commands; and means to effect thesteering of said vehicle in response to said modulated sensOr signal. 2.The steering system of claim 1 wherein said modulating means includesmeans modulating said sensor signal only according to rates of change ofoperator commands above a nominal predetermined rate of change.
 3. Thesteering system of claim 1 wherein said sensor is a vortex rate sensormounted on said vehicle to sense yaw rate of said vehicle.
 4. Thesteering system of claim 3 wherein said modulating means comprisescontrol port means for said vortex rate sensor for influencing an outputflow therefrom according to rates of change of said operator commands.5. The steering system of claim 4 wherein said control port meanscomprises a pair of control ports being tangentially oriented inopposite directions interior of said vortex rate sensor for influencingthe flow therein in opposite rotational directions in accordance withthe direction of said operator commands.
 6. The steering system of claim1 wherein said modulating means comprises: means responsive to saidoperator commands for providing a generated output signal representativeof rates of change of said operator commands; and summing meansassociated with said sensor and said last means for providing saidmodulated signal.
 7. The steering system of claim 6 wherein said summingmeans includes a separate device operatively associated with both saidsensor and said means responsive to rates of change of said operatorcommands for receiving signals therefrom and providing said sum.
 8. Thesteering system of claim 6 wherein said means providing a generatedoutput signal representative of rates of change of said operatorcommands comprises: a housing; dynamic seal means for movement inresponse to said operator commands cooperating with said housing to forma chamber for receiving a fluid; orifice means communicating with saidchamber for providing restricted flow of said chamber fluid therethroughupon movement of said dynamic seal means; and output means communicatingwith said chamber for supplying said generated signal to said summingmeans.
 9. The steering system of claim 8 wherein: said dynamic sealmeans forms two chambers; said orifice means communicates the twochambers, each with the other; and said output means is a pair of flowpassages, each communicating with the pressure in one of said chambers,for supplying said generated signal to said summing means.
 10. A landvehicle steering system which automatically compensates for lateraldisturbances comprising: means for steering said vehicle in response tooperator commands; a fluidic sensor mounted on said vehicle and adaptedto provide a fluid sensor signal representative of course deviations ofsaid land vehicle; means for modulating said sensor signal according tothe rate of change of said operator commands; fluidic amplifier meansfor providing an amplified fluid signal representative of said sum; andmeans to effect the steering of said vehicle in response to saidamplified fluid signal.
 11. The steering system of claim 10 wherein saidmodulating means modulates said sensor signal only according to rates ofchange of operator commands above a nominal predetermined rate ofchange.
 12. The steering system of claim 10 wherein said sensor is avortex rate sensor mounted on said vehicle to sense yaw rate of saidvehicle.
 13. The steering system of claim 12 wherein said modulatingmeans comprises control port means for said vortex rate sensor forinfluencing an output flow therefrom according to rates of change ofsaid operator commands.
 14. The steering system of claim 13 wherein saidcontrol port means comprises a pair of control ports being tangentiallyoriented in opposite directions interior of said vortex rate sensor forinfluencing the flow therein in opposite rotational directions inaccordance with the direction of said operator commands.
 15. Thesteering system of claim 10 wherein said modulating means comprises:means responSive to said operator commands for providing a generatedfluid output signal representative of rates of change of said operatorcommands; and summing means associated with said sensor and said lastmeans for providing said modulated signal.
 16. The steering system ofclaim 15 wherein said summing means includes a separate fluidic deviceoperatively associated with both said sensor and said means responsiveto rates of change of said operator commands for receiving signalstherefrom and providing said sum.
 17. The steering system of claim 15wherein said means providing a generated fluid output signalrepresentative of rates of change of said operator commands comprises: ahousing; dynamic seal means for movement in response to said operatorcommands cooperating with said housing to form a chamber for receiving afluid; orifice means communicating with said chamber for providingrestricted flow of said chamber fluid therethrough upon movement of saiddynamic seal means; and output means communicating with said chamber forsupplying said generated signal to said summing means.
 18. The steeringsystem of claim 17 wherein: said dynamic seal means forms two chambers;said orifice means communicates the two chambers, each with the other;and said output means is a pair of flow passages, each communicatingwith the pressure in one of said chambers, for supplying said generatedsignal to said summing means.
 19. A land vehicle steering system whichautomatically compensates for lateral disturbances comprising: means forsteering said vehicle in response to operator commands; a fluidic sensormounted on said vehicle and adapted to provide a sensor signalrepresentative of course deviations of said land vehicle; means formodulating said sensor signal according to the rate of change ofoperator commands having rates of change above a nominal predeterminedrate of change; means for limiting the response of said system to sensorsignals representative of course deviations having rates of change abovesaid nominal predetermined rate of change; and means for effecting thesteering of said land vehicle according to said modulated sensor signalsto which said system responds.
 20. The steering system of claim 19wherein said sensor is a vortex rate sensor mounted on said vehicle tosense yaw rate of said vehicle.
 21. The steering system of claim 20wherein said modulating means comprises control port means for saidvortex rate sensor for influencing an output flow therefrom according torates of change of said operator commands having rates of change above anominal predetermined rate of change.
 22. The steering system of claim21 wherein said control port means comprises a pair of control portsbeing tangentially oriented in opposite directions interior of saidvortex rate sensor for influencing the flow therein in oppositerotational directions in accordance with the direction of said operatorcommands having rates of change above a nominal predetermined rate ofchange.
 23. The steering system of claim 19 wherein said modulatingmeans comprises: means responsive to said operator commands forproviding a generated output signal representative of rates of change ofsaid operator commands; and summing means associated with said sensorand said last means for providing said modulated signal.
 24. Thesteering system of claim 23 wherein said summing means includes aseparate device operatively associated with both said sensor and saidmeans responsive to rates of change of said operator commands forreceiving signals therefrom and providing said sum.
 25. The steeringsystem of claim 23 wherein said means providing a generated outputsignal representative of rates of change of said operator commandscomprises: a housing; dynamic seal means for movement in response tosaid operator commands cooperating with said housing to form a chamberfor receiving a fluid; orifice means communicating with said chamber forproviding restricted flow of said chamber fluid therethrough uponmovement of said dynamic seal means; and output means communicating withsaid chamber for supplying said generated signal to said summing means.26. The steering system of claim 25 wherein: said dynamic seal meansforms two chambers; said orifice means communicates the two chambers,each with the other; and said output means is a pair of flow passages,each communicating with the pressure in one of said chambers, forsupplying said generated signal to said summing means.